Optical Pixel Architecture With Light Concentration and Deep Isolation
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Solution Overview
Problem
Current digital night vision solutions face challenges in achieving low light performance comparable to analog image intensification (I2) tubes, particularly in extreme low-light conditions, due to high dark current and read noise, which are exacerbated by large pixel sensing regions and shallow trench isolation, leading to image lag and degraded image quality.
Innovation Solution
A pixel architecture with a large optical acceptance aperture and a light concentration structure that directs incident light to a smaller sensing region within a deep-trench-isolation boundary, reducing dark current and read noise, and enabling noise-free 'optical binning' through standard microelectronic manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large pixel sensing region is used, then light collection area is improved, but dark current increases
Solution Approach 1:
The pixel structure is segmented into distinct functional regions: a large optical acceptance aperture for light collection, a smaller sensing region for signal detection, and deep-trench-isolation structures that partition the pixel from neighboring elements. This segmentation allows the optical aperture to be large while the active sensing region remains small, reducing dark current generation area while maintaining light collection efficiency.
Solution Approach 2:
The sensing region is extracted and confined to a small area within the pixel, separated from the larger optical acceptance aperture by the light concentration structure. This extraction allows the sensing region to be minimized for low dark current while the aperture remains large for high light collection, resolving the contradiction between area and dark current.
2Ease of manufacture
If shallow trench isolation is used, then manufacturing simplicity is improved, but pixel-to-pixel crosstalk increases
Solution Approach 1:
The isolation structure employs deep-trench-isolation with different properties at different depths: the upper portion provides basic electrical isolation, while the lower portion extending to the substrate provides enhanced optical isolation. This local quality variation within the isolation structure simultaneously achieves manufacturing feasibility and effective crosstalk reduction.
3Area of stationary object
If a large pixel sensing region is used, then light collection is improved, but image lag increases
Solution Approach 1:
The sensing region is extracted and confined to a small area within the pixel, separated from the larger optical acceptance aperture. This extraction minimizes the distance charge carriers must travel from the light concentration point to the sensing node, reducing image lag while maintaining large aperture area for light collection.
4Measurement precision
If analog binning is used, then low-light sensitivity is improved, but read noise increases
Solution Approach 1:
The optical apertures of multiple pixels are merged through the light concentration structures to focus light onto a single sensing region, achieving optical binning. This merging occurs at the optical level before detection, allowing signal summation without the circuit complexity and associated read noise penalties of electronic binning architectures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the signal-to-noise ratio and reduces dark current and read noise, improving low-light image quality to match or exceed that of I2 tubes, while being more practical and cost-effective, with reduced pixel-to-pixel crosstalk and image lag.
Implementation Method 1
a light concentration structure configured to receive light incident at the optical acceptance aperture and concentrate and direct the received light to the sensing region
Implementation Method 2
the sensing region defined within a border of a first full depth deep-trench-isolation (FDTI)
Data Source
AI summary
A new pixel architecture that enables a reduced dark current and improved signal-to-noise. A light-sensing pixel is configured to have a large optical acceptance aperture, a light concentration structure, and a pixel-sensing area smaller than the optical acceptance aperture, which allows for the collection of more photons without increasing dark current or read noise in the smaller pixel-sensing area. The pixel sensing area may be bordered by a deep trench isolation boundary, which combined with the smaller sensing area, can significantly improve night vision technology, making it more efficient and effective. Certain implementations may also include a metal-filled deep trench isolation boundary around each pixel to eliminate pixel-to-pixel crosstalk.